The invention relates to a plate link chain for infinitely adjustable cone pulley drives, of which the link pivot elements, joining the individual chain links, are embodied in particular as thrust pieces, which with their end faces transmit the frictional forces between the friction disks and the plate link chain and with the link pivot elements inserted into recesses in the plates. Such chains are also known as flat link articulated chains and roller chains. The link pivot elements touch the plate recesses with at least one contacting part of their profile and are secured against escaping sideways out of the plate recesses by at least one securing device.
There are many known forms of link pivot elements for such chains, among them those described in German Pat. Nos. 1 145 871; 1 302 795, 2 356 289; 3 027 834 and U.S. Pat. Nos. 4,500,305; 4,504,255; 4,516,963; 4,516,964; 4,516,965 to name only a few examples. The link pivot elements may be cylindrical link shafts, paired cradle shaft elements, single cradle shaft elements embodying the entire link element, or the like. There is no limitation in this respect in the subject of the present invention.
As for securing the link pivot elements against escaping sideways from the recesses or bores in the plates, the above-mentioned German Pat. Nos. 1 302 795 and 2 356 289 give examples in which, in general terms, bosses or the like are provided on individual plates, or on separately provided securing elements surrounding the link elements; these bosses engage corresponding recesses in the link elements that extend substantially longitudinally of the chain and thereby secure them against lateral movements. Also, U.S. Pat. No. 4,545,779 uses expanded ends of the shaft to prevent movement of the pivot shafts.
This retention of the link elements may be desired or necessary for most various reasons. A primary reason is that the chains are assembled in finished form by the manufacturer and are subsequently moved about, stored, packed and unpacked or otherwise handled while the chain is in an unloaded state prior to finally being used. Since when the chain is assembled the link elements are simply inserted from the side into the plate bores, they can just as easily fall back out of these plate bores while there is no load on the chain, therefore appropriate securing devices are necessary to prevent loss of the link elements.
If the chain is in its installed condition and is under tensile load, then the link elements basically have no tendency to slide sideways out of the plate bores. However, it must not be overlooked that other forces, resulting for instance from vibration, may nevertheless cause the link elements to have a tendency to shift sideways out of the plate bores; given the ensuing realignment when the link elements move in between the cone pulleys, there is a continuous movement back and forth in the plate bores, which causes considerable wear. This situation, as well, is remedied by means of the above-mentioned securing elements.
A similar case arises if the drives are installed with vertically upright axes; then the link elements are likewise disposed substantially vertically, and accordingly, under the influence of gravity, they have a tendency to slide out of the plate bores on one side of the chain.
However, the known securing means or elements as described above are associated with a number of disadvantages, which heretofore were tolerated, because for the reasons given some sort of securing means is indispensable. In particular, the known securing means may hinder automatic chain assembly, or may even make such assembly impossible, because the securing engagement connection between the above-mentioned bosses or the like, on the one hand, and the recesses of the link element, on the other, is attainable only by means of often-complex swiveling movements of the components, or else necessitates assembling the chain while it is in particular curved positions rather than in an extended state. These factors affecting automatic chain assembly become all the more serious given that in the course of modern development the distances between chain links are becoming smaller, and so the number of parts that must be assembled rises accordingly.
Another considerable disadvantage of the known securing means is that the link elements must be provided with recesses for this purpose, as described above, which reduces their cross section; yet this is still another factor of increasing significance in modern chain development, because as chain links become finer and finer, the component parts are becoming smaller and smaller as well. Furthermore, such provisions sometimes result in chain structures that do not allow such securing means at all; one example is German Pat. No. 3 027 834 mentioned above. In such chains, securing means must accordingly be dispensed with entirely, and the danger of sideways shifting of the link pivot elements must somehow be taken into account.